This invention concerns right angle shear presses, sometimes also referred to as corner shear presses.
In a right angle shear, two shear blades are mounted to a holder to extend at right angles to each other, operated with a single actuator such as a hydraulic cylinder.
The shear blade holder is caused to move vertically by operation of the actuator and cause the shear blades to progressively cut a sheet material workpiece along a first or X axis shear blade until contact of the workpiece with a second or Y axis of the shear blades is reached. Thereafter, cutting along the Y axis occurs progressively with further descent of the holder.
The actuator undergoes a complete stroke through a range of motion of the actuator for each cycle of operation of the shear press.
In order to be more flexible, right angle shear presses with back-to-back actuators have been devised in which a short stroke actuator is combined with the main actuator. The short stroke actuator is used to cause only a partial descent of the X axis blade from its fully retracted position, such that the corner formed by the two shear blades does not reach the workpiece. See the corner shear press described in U.S. Pat. No. 3,942,400 as an example. This arrangement enables continuous cutting along the X axis to improve the flexibility in use of the press.
The control of the actuator so as to undergo a full stroke in each press cycle leads to inefficiencies when relatively short dimensioned workpieces are to be produced, as actual cutting takes place for only a fraction of the stroke. Thus, the time and energy required for unneeded segments of the actuation is wasted.